Onchocerciasis focus in Colombia: follow-up study after 12 years.

This study is a follow-up of a 1965 investigation of the only known focus of Onchocerca volvulus in Colombia. In the first phase of the current study, 254 persons were examined. Of the 19 individuals found to be infected with O. volvulus, the youngest was a 16-year-old male. Among those included in the 1965 study, 22 were examined again for microfilariae. Two were positive in both studies, 4 were positive in 1965 but negative in 1977 and the remaining 16 were negative on both occasions. The prevalence of infection, based on identification of microfilariae in skin snips, was lower in the current study (7.5%) than the 15.1% recorded 12 years earlier. However, a 50% response to the Mazzotti test (administration of oral diethylcarbamazine) among a limited number of people upstream from the previously identified endemic area suggests that infection with O. volvulus may be quite widespread.